Generally, a semiconductor wafer W has thereon a plurality of rectangular-shaped semiconductor chips 91 (FIG. 9A). Each of the semiconductor chips 91 is provided with about 100 to about 500 rectangular-shaped electrode pads 92 (FIG. 9B). In order to guarantee quality of a semiconductor chip 91, electrical characteristics of the semiconductor chip 91 are tested before it is cut out from a semiconductor wafer W.
In order to test the electrical characteristics of the semiconductor chip 91, a needle-shaped testing probe 93 contacts with each of the electrode pads 92 of the corresponding semiconductor chip 91 (FIG. 9C). Here, the electrode pad 92 is generally made of a thin aluminum film, so that a surface thereof is made to be coated with an insulating aluminum oxide film formed by natural oxidation. Accordingly, in order to make the testing probe 93 pass through the aluminum oxidation film, a specific level of force is applied when the testing probe 93 contacts with the electrode pad 92. As a result, a needle mark 94 is formed on the electrode pad 92 by the testing probe 93 (FIG. 9D). By checking whether the needle mark 94 exists or not and also by checking a position, a depth or the like thereof, it is determined whether or not the testing probe 93 has accurately contacted with the electrode pad 92.
If the testing probe 93 contacts with the electrode pad 92 multiple times, a hole may be formed on the electrode pad 92 made of the thin aluminum film. To that end, the testing probe 93 needs to contact with the electrode pad 92 while avoiding previously formed needle marks 94. Therefore, before testing the electrical characteristics of the semiconductor chip 91, it is required to check the positions or the like of the needle marks 94 on each of the electrode pads 92 (needle mark inspection).
As for a method for efficiently performing the needle mark inspection, there is known a method for checking positions or the like of needle marks by following procedures: consecutively moving a stage for mounting thereon a semiconductor wafer until a focus of a camera disposed to face the stage becomes close to electrode pads; illuminating the electrode pads by flashlight of the camera when the focus of the camera is close to the electrode pads; capturing images of the electrode pads; and analyzing the captured images of the electrode pads (see, e.g., Japanese Patent Laid-open Application No. 2005-45194). In order to implement this method, it is required to detect or recognize in advance the positions of the electrode pads.
As for a conventional method for detecting or recognizing positions of electrode pads, there is known a method for capturing an image of a semiconductor wafer by a camera and enlarging the captured image to thereby define positions of electrode pads on the corresponding image by using a pointing device such as a mouse or the like, or a method for inputting position coordinate data of electrode pads on each semiconductor chip to an inspection device for performing needle mark inspection.
Recently, due to an increase of inspection items in the electrical characteristics test, a semiconductor chip inspection is performed by an inspection company (test house) different from a semiconductor chip manufacturing company. However, position data of electrode pads are generally not included in semiconductor chip data supplied from the manufacturing company to the inspection company. Therefore, the inspection company uses the former method to define positions of electrode pads on an image.
Meanwhile, a single semiconductor chip has about 100 to about 500 electrode pads, so that the operation of defining positions of electrode pads on an image requires a considerable amount of labor from an operator. As a result, it is difficult to detect the positions of all the electrode pads of the semiconductor chip.